Abstract
The aim of the present study was to compare the selection performed by the sum of standardized variables index (Z Index) with the selection based only on the grain yield character, to verify if the grain yield alone is a good alternative for the selection involving multiple characters. The experiments were conducted in Lavras-MG and in Lambari-MG, during the 2015/2016 agricultural year. The used design was the randomized complete block design with 3 replications. Thirty-six genotypes of the preliminary trial of upland rice breeding program of the Federal University of Lavras were evaluated. In order to compose the Z index, the following characteristics were evaluated: grain yield, height, number of days for flowering, 1000-grain weight, income, yield, leaf blast incidence, and grain length/width ratio. Z index was efficient in the selection for multiple characters whereas not all lines with the highest grain yield obtained good results in the other desirable characteristics, indicating that the selection based only on grain yield is not efficient when working with several characters of interest in upland rice cultivation.
Highlights
In order to launch an upland rice cultivar, the breeder must associate a number of desirable traits that provide high yield and meet market requirements
One option is to use the simultaneous selection of the characters involved, through the use of selection indexes, which combine the information of all the characters, so that the selection is based on a single value involving all the others (Ramalho et al, 2012)
This paper aimed to compare the selection performed by the Z index with the selection through the grain yield character, to verify if the grain yield alone is a good alternative for the selection involving multiple characters in upland rice
Summary
In order to launch an upland rice cultivar, the breeder must associate a number of desirable traits that provide high yield and meet market requirements. In addition to grain yield, a good rice cultivar must associate characteristics that facilitate cultural treatments and provide good industrial and culinary quality. Handling multiple characters at the same time and efficiently is a great challenge and the breeder must always be looking for alternatives that facilitate selection, but at the same time promote the selection of desirable genotypes effectively. Several methodologies of selection indexes are found in the literature, among them the sum of standardized variables index (Z Index), in this index the character data are standardized to make them directly comparable (Nunes et al, 2005). Good results were obtained in beans (Mendes, 2009; Lima, 2015) and eucalyptus (Reis, 2015) with the use of this method
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